1. Field of the Invention
This inventions relates, in general, to hydraulic couplings, and specifically to hydraulic couplings used in undersea drilling and production applications. More particularly, the invention involves a member of a subsea hydraulic coupling capable of bleeding off hydraulic pressure when it is disconnected from the corresponding coupling member.
2. Description of Related Art
Subsea hydraulic couplings are old in the art. The couplings generally consist of a male member and a female member with sealed fluid passageways connecting therebetween. The female member generally is a cylindrical body with a relatively large diameter longitudinal bore, or receiving chamber, at one end and a relatively small diameter longitudinal bore at the other. The small bore facilitates connections to hydraulic lines, while the larger bore seals and slidingly engages the male member of the coupling. The male member includes a cylindrical portion at one end having an outer diameter approximately equal to the diameter of the large bore in the female member of the coupling. The male member also includes a connection at its other end to facilitate connection to hydraulic lines. When the cylindrical portion of the male member is inserted into the large bore of the female member, according to various embodiments of the device, fluid flow is established between the male and female members.
The male and female members of a hydraulic coupling each typically include a poppet valve slidably received within the bore of each member. Each poppet valve typically includes a conical valve face which seats, in the closed position, against a valve seat in the bore. The poppet valve opens to allow fluid flow, and closes the poppet valve face against the corresponding valve seat within the bore to arrest the flow. Generally the poppet valve is spring-biased to the closed position. The valve also includes a valve actuator which may be a nose or stem extending from the apex of the valve face along the longitudinal axis of the poppet valve. Contact between the valve actuators of the male and female member poppet valves forces each valve face away from the valve seat and into the open position for fluid flow between the members. Some undersea coupling members do not have valve actuators, but instead utilize valves that open in response to fluid pressure from the opposing coupling member.
Typically, the male members and female members are attached to opposing manifold plates. In emergency situations, for example, storms, fires, hurricanes, etc., the manifold plates are quickly separated and the male and female members are disconnected. When the male and female members are disconnected, particularly in emergency situations, problems arise as a result of trapped hydraulic pressure in the lines. Safety valves in the subsea hydraulic systems are typically designed to close when hydraulic pressure in the system drops below a predetermined pressure. If hydraulic pressure is trapped subsea, safety valves in the hydraulic systems have a tendency to remain open due to the remaining pressure in the lines. It is undesirable for the safety valve to remain open due to trapped pressure, so to relieve the pressure, it has been suggested to bleed the hydraulic lines that are trapped subsea. Bleeding the lines also is done to avoid damage from blowouts to the hydraulic system. Therefore, if the hydraulic system is in danger of being severed or otherwise damaged due to storms, it then is desirable to disconnect the members and check off or seal one member while allowing the other member, which remains subsea, to bleed off trapped hydraulic pressure. At the same time, it is undesirable for seawater to enter the system through the coupling member that remains subsea.
Bleeding off of trapped hydraulic pressure solves the problem of dangerous high pressure in the hydraulic system which often may result in blowouts to the hydraulic system or safety valves failing to close when the couplings are disconnected. Preferably, to prevent seawater from entering the hydraulic system during bleeding, the bleed passage should include a check valve which permits flow in one direction only. The present invention solves all of these needs and requirements.
In U.S. Pat. No. 5,365,972 to Robert E. Smith III assigned to National Coupling Company, Inc. of Stafford, Tex., an undersea hydraulic coupling is shown, with at least one of the members having a bleed passage through the poppet valve and a bleed valve which opens to allow hydraulic pressure to escape through the bleed passage until the pressure is below a predetermined amount. The coupling of U.S. Pat. No. 5,365,972 discloses a bleed valve that slides within a sleeve in one of the coupling members. When the bleed valve opens due to excess line pressure, hydraulic fluid flows through the bleed valve, the sleeve and out a passage in the poppet valve of the member. The coupling of U.S. Pat. No. 5,365,972 discloses a pair of valves in the coupling member to facilitate bleeding hydraulic fluid that is trapped in the lines.
The present invention resides in a hydraulic coupling member of the foregoing type, that bleeds off trapped hydraulic fluid pressure when the member is disconnected from the corresponding coupling member. The present invention involves a bleeding mechanism using a sleeve in the coupling member and a poppet valve in the sleeve which allows trapped hydraulic fluid at high pressure to escape until the hydraulic pressure is decreased to a predetermined pressure. The present invention keeps seawater intrusion out of the lines in subsea equipment, thereby preventing contamination and corrosion.